The present invention relates to a coin diameter discriminating device for discriminating the diameters of coins inserted in a public telephone or the like.
In a conventional method, a coin discriminating device used for, e.g., a public telephone, employs coils for coin material and thickness discrimination so as to discriminate the physical characteristics of coins. In this method, however, since diameter data of coins cannot be obtained, coins consisting of the same material and having different diameters cannot be discriminated. Japanese Patent Laid-Open No. 54-41766, therefore, discloses a device in which optical sensors ar arranged to be separated from each other in the rolling direction of coins. This device discriminates the diameter of a coin on the basis of the time during which light emitted from each optical sensor is shielded by the coin passing therethrough.
In such a conventional device, however, two different optical sensors need to be arranged in the rolling direction of coins. Since the speed of a coin is higher at the instant when passing through the second sensor than the instant when passing through the first sensor, an error due to variations in diameters of coins cannot be prevented. In addition, since at least two types of sensors must be arranged in the rolling direction of coins, the distance required for discrimination cannot be satisfactorily shortened, thereby posing a problem in terms of compactness.